Interactive virtual reality display providing accommodation depth cues

ABSTRACT

An interactive display includes a display capable of generating displayed images, and first and second eyepiece assemblies each including one or more variable-focus lenses. The eyepiece assemblies, variable-focus lenses and display allow the user to perceive a virtual 3D image while providing visual depth cues that cause the eyes to accommodate at a specified fixation distance. The fixation distance can be adjusted by changing the focal power of the variable-focus lenses.

PRIORITY CLAIM

This application claims the priority benefit of U.S. Provisional PatentApplication No. 62/326,677 filed Apr. 22, 2016, the entire contents ofwhich are incorporated herein by reference for all purposes.

BACKGROUND

Head mounted displays (HMDs) for virtual reality, and more recentlyaugmented reality, were first developed as early as the 1660's and havebeen improved upon in waves of technological development. The basicpurpose of a HMD is to exploit the stereo nature of human visualperception to create a virtual 3D environment. The general approachemployed by many current HMDs consists of a stereo pair of displays(LCD, LED, OLED, etc.) with an eyepiece lens disposed in front of eachdisplay, proximal to the eye of the user. The purpose of the eyepiecelenses is to create a virtual stereo 3D image from the displays, whichappears to be located at a comfortable distance in front of the user'seyes so as to reduce eye strain. The effect of seeing a stereo 3D imageis predominantly based on two physiological cues, stereopsis andvergence. Stereopsis is the difference between the scenes viewed by eacheye, and vergence is the pointing of the eyes so that both are lookingat the same point in space, or fixation point. The primary limitation tothis type of display system is its failure to provide a third importantphysiological depth cue, accommodation. Accommodation is associated withthe change in optical power of the human eye. As a person looks atobjects which are different distances away, their eyes “accommodate” sothat the objects they are looking at are in focus. In current typicalHMDs, the user's eyes aren't provided cues to change accommodation andtherefore are statically focused on the virtual image plane of thedisplay, located at a fixed distance from the user as viewed through theeyepiece lenses. Virtual images which provide stereopsis and vergence,but not accommodation, may present a mismatch or ambiguity of visualdepth cues to the user. This mismatch may cause a reduction in realismof the displayed image (in large part because all objects beingdisplayed appear to be “in focus” regardless of distance from the user).Additionally, the user may suffer eye strain as the eyes are beingforced to respond to the displayed imagery in an unnatural way, withoutthe physiological function of accommodation.

BRIEF DESCRIPTION OF INVENTION

Aspects of the present disclosure overcome the limitations of existingtechnology by enabling HMDs with accurate accommodation depth cues,providing more realistic imagery and more comfortable use. According toan aspect of the present disclosure, an HMD for virtual reality oraugmented reality applications uses variable focus lenses to provideaccurate accommodation cues. In some embodiments the system may alsoinclude eye tracking capability to determine the proper focal power ofthe variable focus lenses.

BRIEF DESCRIPTION OF THE FIGURES

Objects and advantages of aspects of the present disclosure will becomeapparent upon reading the following detailed description and uponreference to the accompanying drawings in which:

FIG. 1 depicts a variable collimation head mounted display exploded,labeled

FIG. 2 is a schematic drawing of a moving virtual 3D image plane

FIG. 3 is an exploded view of a variable-focus lens

FIG. 4 is a top view of a variable-focus lens

FIG. 5 is a cross-sectional view of a variable-focus fluidic lens

DETAILED DESCRIPTION OF FIGURES

Although the following detailed description contains many specificdetails for the purposes of illustration, anyone of ordinary skill inthe art will appreciate that many variations and alterations to thefollowing details are within the scope of the invention. Accordingly,the aspects of the disclosure described below are set forth without anyloss of generality to, and without imposing limitations upon, theclaimed invention.

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof, and in which is shownby way of illustration specific embodiments in which the invention maybe practiced. In this regard, directional terminology, such as “top,”“bottom,” “front,” “back,” “first,” “second,” etc., is used withreference to the orientation of the figure(s) being described. Becausecomponents of embodiments of the present invention can be positioned ina number of different orientations, the directional terminology is usedfor purposes of illustration and is in no way limiting. It is to beunderstood that other embodiments may be utilized and structural orlogical changes may be made without departing from the scope of thepresent invention. The following detailed description, therefore, is notto be taken in a limiting sense, and the scope of the present inventionis defined by the appended claims.

FIG. 1 depicts an embodiment of a head mounted display (HMD), and morespecifically, a variable accommodation HMD (VAHMD) device 100 accordingto the present invention. VAHMD 100 comprises a faceplate 110, a housing170 which encloses first and second eyepiece assemblies, e.g., a lefteyepiece assembly 120, and a right eyepiece assembly 130, respectively.Eyepiece assembly comprises an eye tracker 180, static lens 140,variable-focus lens 150, and display 160. Display 160 may be include anynumber of types of displays including but not limited to: LCD, OLED,LED-LCD, waveguide illuminated, holographic, light field, transparent,projected, direct retinal, or scanned laser. In some embodiments, theleft and right eyepiece assemblies 120, 130 may share a single display.In an alternative embodiment, eye tracker 180 and/or static lens 140 maybe integrated into variable focus lens 150. Alternatively, eye tracker180 may be disposed separately from eyepiece assembly 130. In someimplementations, the separation between the eyepiece assemblies 120, 130can be adjustable to match the user's interpupillary distance. Staticlens 140 may include any type of refractive or diffractive lens, prism,mirror or array thereof, including without limitation arrays ofmicrolenses.

FIG. 2 shows a schematic drawing of one embodiment of VAHMD 100.Eyepiece assemblies 120, 130 are disposed between the user's eyes 200and display 160 and configured so that the user perceives a virtualstereo 3D image located at a virtual distance away. To ensure that theaccurate accommodation visual cues are provided to the user, the virtualdistance must be substantially identical to the user's natural fixationdistance (i.e., the distance from the user's eyes to the fixation pointin space) based on the scene being viewed. In some embodiments, theuser's fixation distance may be determined by measuring the 3Dcoordinates of the user's fixation point with eye tracker 180.Alternatively, the user's fixation point or fixation distance may bedetermined by any other type of positional sensor, including but notlimited to: integrated inertial measurement unit (IMU), integratedgyroscope, external optical tracking devices and methods, integratedtime of flight sensor, simultaneous localization and measurement (SLAM)imaging system, or using the content of the displayed virtual image toencourage user to fixate (or, gaze) on a specific point. The virtualdistance is controlled by adjusting the optical power of one or morevariable-focus lenses 150. For example, FIG. 2a shows an example of avariable-focus lens 150 in a first state of actuation, causing a virtualstereo 3D image to appear at first specified virtual distance 210.Likewise, FIG. 2b shows an example of a variable-focus lens 150 in asecond state of actuation, causing a virtual stereo 3D image to appearat a second specified virtual distance 220. In one embodiment, acontroller, such as a computer or processor (not shown), is connected toVAHMD 100. The controller serves to interpret data from eye tracker 180and provide control signals to the variable-focus lens(es) 150. Thecontroller is configured in such a fashion that control signals serve tomodify the optical properties of the eyepiece assembly 120 and variablefocus lens(es) 150 so that the virtual distance is adjusted to besubstantially identical to the fixation distance. In other embodimentsthe controller may be a processor (not shown) embedded in the VAHMD 100.Variable-focus lens(es) 150 may include any of the following group:lenses configured to have tunable focal power, fluidic lenses, liquidlenses, adaptive lenses, electrowetting lenses, liquid crystal lenses,mechanically moving lenses and autofocus lenses, lenses configured tohave tunable tilt, switchable holographic optical elements, switchablediffractive optical elements, arrays of variable-focus microlenses, orany other technology for controlling the focal power, tilt, aperturesize, or other optical property of a lens. In another embodiment,variable-focus lens(es) 150 may be disposed between display 160 and apartially reflective mirror (not shown) through which users eyes 200 mayview the world while simultaneously viewing reflected imagery fromdisplay 160 to form an augmented reality display.

FIG. 3 shows an exploded view of an example of a possible implementationof a variable-focus lens 150. In this example, the variable-focus lens150 comprises a fluid chamber 360 substantially filled with a lens fluid370, lens body 320, window 330, and membrane 310. In some embodiments,lens fluid 370 may be replaced by any other optical medium such as a gelor polymer. Lens body 320 encapsulated lens chamber 360. Variable-focuslens 150 may also include a displacement plate 300 configured to depress(i.e., apply an actuation force to) a portion of membrane 310.Depressing of membrane 310 by displacement plate 300 results in theactuation of variable-focus lens 150 and a corresponding change in itsoptical properties, such as focal power, from a first (non-actuated)state to second (actuated) state. Membrane 310 may be configured so thatupon release of actuation force, variable-focus lens 150 returns fromsecond (actuated) state to first (non-actuated) state. Displacementplate 300 may be controlled by movement of magnet 340 within solenoid350. In a preferred embodiment of the present invention, window 330,membrane 310, and lens fluid 370 substantially transparent to light inthe visible and/or infrared spectrum. Alternatively, window 330,membrane 310, and lens fluid 370 may be transparent to wavelengths oflight in other portions of the electromagnetic spectrum. In otherembodiments, magnet 340 and solenoid 350 may be replaced with any otherform of actuator, such as a piezoelectric, MEMS, electrostatic,electroactive polymer, electric motor, ultrasonic motor, stepper motor,or pump, and appropriate mechanical linkages as will be generallyunderstood by those skilled in the art of variable-focus lenses.

FIG. 4 shows a top view of the variable-focus lens depicted in FIG. 3.The variable focus lens has a clear aperture 420 and mounting holes 410.When variable-focus lens 150 is actuated, the portion of membrane 310within clear aperture 420 is configured to deform in a generallyspherical manner causing the focal power of variable-focus lens 150 tochange from first state to second state.

FIG. 5 shows a cross-sectional view of the variable-focus lens depictedin FIG. 3 and FIG. 4. Solenoid 350 is comprised of bobbin 500 and coils510. The position of magnet 340 within bobbin 500 is dependent on theamount of electrical current, produced by a power source (not shown),flowing through coils 510. Magnet 340 is disposed in communication withdisplacement plate 300 in such a fashion that a movement of magnet 340causes a translation of displacement plate 300 and a correspondingdeformation of membrane 310 in the area outside clear aperture 420 (notshown). As the portion of membrane 310 outside clear aperture 420 (notshown) is deformed, the fluid 370 within fluid chamber 360 is alsodisplaced, causing a substantially spherical deformation of a portion ofmembrane 310 located within clear aperture 420 and a correspondingchange in the focal power of variable-focus lens 150. As is generallyunderstood by those skilled in the optical arts, the term “clearaperture” (also known as free aperture or objective aperture) refers tothe limited light-gathering area of an optical system. The area isnormally restricted to an edge or outer surface of an individualcomponent.

By way of example, and not by way of limitation, the clear aperture of alens in most lens drawings refers to the full diameter of the lensthrough which light can pass.

While the above is a complete description of the preferred embodiment ofthe present invention, it is possible to use various alternatives,modifications and equivalents. Therefore, the scope of the presentinvention should be determined not with reference to the abovedescription but should, instead, be determined with reference to theappended claims, along with their full scope of equivalents. In theclaims that follow, the indefinite article “A”, or “An” refers to aquantity of one or more of the item following the article, except whereexpressly stated otherwise. The appended claims are not to beinterpreted as including means-plus-function limitations, unless such alimitation is explicitly recited in a given claim using the phrase“means for.” Any feature described herein, whether preferred or not, maybe combined with any other feature, whether preferred or not.

The invention claimed is:
 1. An interactive virtual reality displaywhich provides accurate accommodation visual cues to a user comprising;one or more display, capable of generating one or more displayed image;a first eyepiece assembly and second eyepiece assembly wherein eacheyepiece assembly includes one or more variable-focus lenses, eachvariable focus lens having a clear aperture, wherein each of the one ormore variable-focus lenses includes a mounting hole that is separatefrom the clear aperture and smaller than the clear aperture, a lens bodyfilled with a lens fluid disposed between a transparent membrane and atransparent window, and a displacement plate configured to impinge on aportion of the membrane outside the clear aperture of the variable focuslens in response to an actuation force from an actuator so thattranslation of the displacement plate causes a corresponding deformationof the transparent membrane in an area outside the clear aperture andcauses a change in curvature of the transparent membrane therebychanging the focal properties of the variable-focus lens; wherein thefirst and second eyepiece assemblies are configured to be disposedbetween the display and first and second eyes of the user, respectively,when the virtual reality display is in use; wherein the first and secondeyepiece assemblies and display are configured to allow the user toperceive a virtual 3D image of the displayed image; wherein the userperceives the virtual 3D image to be located a virtual distance awayfrom the user; wherein the first and second eyepiece assemblies areconfigured such that a focus adjustment of one or more variable-focuslens results in an adjustment of the virtual distance; and wherein 3Dcoordinates of a fixation point located a fixed distance away from theuser are used to control one or more of the first and secondvariable-focus lenses in such a manner that the first and secondeyepiece assemblies adjust to control the virtual distance of thevirtual 3D image.
 2. The system of claim 1, further comprising an eyetracking system capable of determining the 3D coordinates of thefixation point of the user.
 3. The system according to claim 1 wherein apartially reflective mirror or beam splitter is placed between thevariable focus lenses and the user's eyes so as to allow the user tosimultaneously view the real world and the virtual imagery from thedisplay.
 4. The system according to claim 1 wherein the virtual distanceof the virtual 3D image is controlled to be identical to the fixationdistance of the user.
 5. The system according to claim 1 wherein thevirtual distance of the virtual 3D image is controlled to be differentthan the fixation distance of the user.
 6. The system according to claim1 wherein the variable-focus lenses have a thin form factor to integratewell into a head mounted display device.
 7. The system according toclaim 1 wherein the body of the variable-focus lens is non-planar and isconformal to the shape of a human head and the curvature of a headmounted display.
 8. The system according to claim 1 wherein the variablefocus lenses may be independently controlled from each other.
 9. Thesystem from claim 1 wherein the eyepiece assemblies comprise one or morestatic lens and one or more variable-focus lens.
 10. The system in claim1 wherein the separation between the eyepiece assemblies can be adjustedto match the user's interpupillary distance.
 11. The system in claim 1wherein a portion of the variable-focus lens is integrated into thetemples of a head mounted display.
 12. The system from claim 1 whereinthe actuator is an electromagnetic actuator.
 13. The system from claim 1wherein the actuator is a piezoelectric actuator.
 14. The system fromclaim 1 wherein the actuator is an electric motor.
 15. The system fromclaim 1 wherein the interactive virtual reality display is part of ahead-mounted display (HMD) that can be worn by the user.
 16. The systemfrom claim 1 wherein one or more static lens is integrated into the lensbody of the variable-focus lens to make an integral optical element. 17.An interactive virtual reality display which provides accurateaccommodation visual cues to a user comprising; one or more display,capable of generating one or more displayed image; a first eyepieceassembly and second eyepiece assembly wherein each eyepiece assemblyincludes a variable-focus lens, wherein each of the one or morevariable-focus lenses includes a clear aperture and a mounting hole,wherein the mounting hole is separate from the clear aperture andsmaller than the clear aperture, a lens body filled with a lens fluiddisposed between a transparent membrane and a transparent window, and adisplacement plate configured to impinge on a portion of the membraneoutside a clear aperture of the variable-focus lens in response to anactuation force from an actuator so that translation of the displacementplate causes a corresponding deformation of the transparent membrane inan area outside the clear aperture and causes a change in curvature ofthe transparent membrane thereby changing in the focal properties of thevariable-focus lens; wherein the first and second eyepiece assembliesare configured to be disposed between the display and first and secondeyes of the user, respectively, when the virtual reality display is inuse; wherein the first and second eyepiece assemblies and display areconfigured to allow the user to perceive a virtual 3D image of thedisplayed image; wherein the user perceives the virtual 3D image to belocated a virtual distance away from the user; and wherein the first andsecond eyepiece assemblies are configured such that a focus adjustmentof one or more variable-focus lens results in an adjustment of thevirtual distance.
 18. The system from claim 17 further comprising an eyetracking system capable of determining the 3D coordinates of thefixation point of the user; wherein the fixation point is located at afixation distance away from the user; and wherein the 3D coordinates ofthe fixation point are used to control one or more of the first andsecond variable-focus lenses in such a manner that the first and secondeyepiece assemblies adjust to control the virtual distance of thevirtual 3D image.